Camptothecin and its analogues: a review on their chemotherapeutic potential

Stain-Free Approach to Determine and Monitor Cell Heath Using Supervised and Unsupervised Image-Based Deep Learning

Cell-based medicinal products (CBMPs) are a growing class of therapeutics that promise new treatments for complex and rare diseases. Given the inherent complexity of the whole human cells comprising CBMPs, there is a need for robust and fast analytical methods for characterization, process monitoring, and quality control (QC) testing during their manufacture. Existing techniques to evaluate and monitor cell quality typically constitute labor-intensive, expensive, and highly specific staining assays. In this work, we combine image-based deep learning with flow imaging microscopy (FIM) to predict cell health metrics using cellular morphology "fingerprints" extracted from images of unstained Jurkat cells (immortalized human T-lymphocyte cells). A supervised (i.e., algorithm trained with human-generated labels for images) fingerprinting algorithm, trained on images of unstained healthy and dead cells, provides a robust stain-free, non-invasive, and non-destructive method for determining cell viability. Results from the stain-free method are in good agreement with traditional stain-based cytometric viability measurements. Additionally, when trained with images of healthy cells, dead cells and cells undergoing chemically induced apoptosis, the supervised fingerprinting algorithm is able to distinguish between the three cell states, and the results are independent of specific treatments or signaling pathways. We then show that an unsupervised variational autoencoder (VAE) algorithm trained on the same images, but without human-generated labels, is able to distinguish between samples of healthy, dead and apoptotic cells along with cellular debris based on learned morphological features and without human input. With this, we demonstrate that VAEs are a powerful exploratory technique that can be used as a process monitoring analytical tool.

Development of an ELISA with acidification treatment for an antibody conjugate incorporating Exatecans

The successful development of Sacituzumab Govitecan and Trastuzumab Deruxtecan has made camptothecin derivatives one of the most popular payloads for antibody-drug conjugates (ADCs). Camptothecin and its derivatives all exist in a pH-dependent equilibrium between the carboxylate and lactone forms. Such transformation may lead to differences in the ratio of the two molecular forms in calibration standards and biological matrix (bio-matrix) samples, thereby leading to inaccurate conjugated antibody results. In this study, we reported an enzyme-linked immunosorbent assay (ELISA) free of the aforementioned influence for the detection of the Exatecans-conjugated antibody (conjugated SM001) in cynomolgus monkey serum. The assay was developed by first acidifying all samples with glacial acetic acid (HAc), then performing neutralization and thereafter capturing conjugated SM001 with anti-Exatecan monoclonal antibody (mAb) and detecting it with biotinylated Nectin4 (hNectin4-Bio) and horseradish peroxidase-labeled streptavidin (SA-HRP). Results showed that all tested performance parameters met the acceptance criteria. The conjugated SM001 concentrations obtained were in parallel to but slightly lower than total antibody (TAb) throughout the pharmacokinetic (PK) study, revealing that the assay strategy implemented for conjugated SM001 measurement worked well for the elimination of interference triggered by the heterogeneous existence of the lactone and carboxylate forms of Exatecan (lactone-Exatecan and carboxylate-Exatecan).

Small Molecule-Drug Conjugates: Opportunities for the Development of Targeted Anticancer Drugs

Conventional chemotherapy is insufficient for precise cancer treatment due to its lack of selectivity and inevitable side effects. Targeted drugs have emerged as a promising solution for precise cancer treatment. A common strategy is to conjugate therapeutic agents with ligands that can specifically bind to tumor cells, providing targeted therapy. Similar to the more successful antibody drug conjugates (ADCs), small molecule drug conjugates (SMDCs) are another promising class of targeted drugs, consisting of three parts: targeting ligand, cleavable linker and payload. Compared to ADCs, SMDCs have the advantages of smaller size, better permeability, simpler preparation process and non-immunogenicity, making them a promising alternative to ADCs. This review describes the characteristics of the targeting ligand, linker and payload of SMDCs and the criteria for selecting a suitable one. We also discuss recently reported SMDCs and list some successful SMDCs that have entered clinical trials.

A review on endophytic fungi: a potent reservoir of bioactive metabolites with special emphasis on blight disease management

Phytopathogenic microorganisms have caused blight diseases that present significant challenges to global agriculture. These diseases result in substantial crop losses and have a significant economic impact. Due to the limitations of conventional chemical treatments in effectively and sustainably managing these diseases, there is an increasing interest in exploring alternative and environmentally friendly approaches for disease control. Using endophytic fungi as biocontrol agents has become a promising strategy in recent years. Endophytic fungi live inside plant tissues, forming mutually beneficial relationships, and have been discovered to produce a wide range of bioactive metabolites. These metabolites demonstrate significant potential for fighting blight diseases and provide a plentiful source of new biopesticides. In this review, we delve into the potential of endophytic fungi as a means of biocontrol against blight diseases. We specifically highlight their significance as a source of biologically active compounds. The review explores different mechanisms used by endophytic fungi to suppress phytopathogens. These mechanisms include competing for nutrients, producing antifungal compounds, and triggering plant defense responses. Furthermore, this review discusses the challenges of using endophytic fungi as biocontrol agents in commercial applications. It emphasizes the importance of conducting thorough research to enhance their effectiveness and stability in real-world environments. Therefore, bioactive metabolites from endophytic fungi have considerable potential for sustainable and eco-friendly blight disease control. Additional research on endophytes and their metabolites will promote biotechnology solutions.

Development and Validation of an ADA-Tolerant Assay for Quantification of an Exatecan-Based ADC in Monkey Plasma

BACKGROUND

The development of an anti-drug antibody (ADA)-tolerant pharmacokinetic (PK) assay is important when the drug exposure is irrelevant to toxicity in the presence of ADA. We aimed to develop and validate an ADA-tolerant assay for an exatecan-based antibody-drug conjugate (ADC) in monkey plasma.

RESULTS

The assay tolerated 5.00 µg/mL of ADA at 12 µg/mL of ADC. Its accuracy and precision results satisfied the acceptance criteria. Furthermore, the assay was free from hook and matrix effects and exhibited good dilutional linearity. Additionally, the ADC in plasma samples was stable under different storage conditions.

METHOD

An ADA-tolerant ADC assay was configured with an anti-payload antibody for capture, and a drug-target protein combined with a horseradish peroxidase (HRP)-labeled antibody against a drug-target-protein tag for detection. Samples were firstly acidified to dissociate drug and ADA complexes, and to convert the carboxylate form to the lactone form of exatecan molecules; then, the ADAs in the samples were removed with a naked antibody-coated microplate. The treated samples were further incubated with coated anti-payload antibody and captured ADC molecules were quantified by the detection reagent. The developed assay was optimized and validated against regulatory guidelines.

CONCLUSIONS

The assay met both methodological and sample-related ADA tolerance requirements, and was applicable to a nonclinical study in cynomolgus monkeys.

Sensitive monitoring of NAD(P)H levels within cancer cells using mitochondria-targeted near-infrared cyanine dyes with optimized electron-withdrawing acceptors

A series of near-infrared fluorescent probes, labeled A to E, were developed by combining electron-rich thiophene and 3,4-ethylenedioxythiophene bridges with 3-quinolinium and various electron deficient groups, enabling the sensing of NAD(P)H. Probes A and B exhibit absorptions and emissions in the near-infrared range, offering advantages such as minimal interference from autofluorescence, negligible photo impairment in cells and tissues, and exceptional tissue penetration. These probes show negligible fluorescence when NADH is not present, and their absorption maxima are at 438 nm and 470 nm, respectively. In contrast, probes C-E feature absorption maxima at 450, 334 and 581 nm, respectively. Added NADH triggers the transformation of the electron-deficient 3-quinolinium units into electron-rich 1,4-dihydroquinoline units resulting in fluorescence responses which were established at 748, 730, 575, 625 and 661 for probes AH-EH, respectively, at detection limits of 0.15 μM and 0.07 μM for probes A and B, respectively. Optimized geometries based on theoretical calculations reveal non-planar geometries for probes A-E due to twisting of the 3-quinolinium and benzothiazolium units bonded to the central thiophene group, which all attain planarity upon addition of hydride resulting in absorption and fluorescence in the near-IR region for probes AH and BH in contrast to probes CH-EH which depict fluorescence in the visible range. Probe A has been successfully employed to monitor NAD(P)H levels in glycolysis and specific mitochondrial targeting. Furthermore, it has been used to assess the influence of lactate and pyruvate on the levels of NAD(P)H, to explore how hypoxia in cancer cells can elevate levels of NAD(P)H, and to visualize changes in levels of NAD(P)H under hypoxic conditions with CoCl2 treatment. Additionally, probe A has facilitated the examination of the potential impact of chemotherapy drugs, namely gemcitabine, camptothecin, and cisplatin, on metabolic processes and energy generation within cancer cells by affecting NAD(P)H levels. Treatment of A549 cancer cells with these drugs has been shown to increase NAD(P)H levels, which may contribute to their anticancer effects ultimately leading to programmed cell death or apoptosis. Moreover, probe A has been successfully employed in monitoring NAD(P)H level changes in D. melanogaster larvae treated with cisplatin.

Advanced application of nanotechnology in active constituents of Traditional Chinese Medicines

Traditional Chinese Medicines (TCMs) have been used for centuries for the treatment and management of various diseases. However, their effective delivery to targeted sites may be a major challenge due to their poor water solubility, low bioavailability, and potential toxicity. Nanocarriers, such as liposomes, polymeric nanoparticles, inorganic nanoparticles and organic/inorganic nanohybrids based on active constituents from TCMs have been extensively studied as a promising strategy to improve the delivery of active constituents from TCMs to achieve a higher therapeutic effect with fewer side effects compared to conventional formulations. This review summarizes the recent advances in nanocarrier-based delivery systems for various types of active constituents of TCMs, including terpenoids, polyphenols, alkaloids, flavonoids, and quinones, from different natural sources. This review covers the design and preparation of nanocarriers, their characterization, and in vitro/vivo evaluations. Additionally, this review highlights the challenges and opportunities in the field and suggests future directions for research. Nanocarrier-based delivery systems have shown great potential in improving the therapeutic efficacy of TCMs, and this review may serve as a comprehensive resource to researchers in this field.

The recent developments of camptothecin and its derivatives as potential anti-tumor agents

This review article focuses on the research progress made in the structural modifications of camptothecin (CPT), a potent cytotoxic natural alkaloid. CPT possesses a unique 5-fused ring structure and exhibits various beneficial activities such as anti-proliferative, anti-fungal, insecticidal, and anti-SARS-CoV-2 properties. CPT and its analogs, including Topotecan and Irinotecan, have been successfully developed and marketed as topoisomerase I inhibitors. To enhance the therapeutic potential of CPT, researchers have undertaken structural modifications primarily on the A, B, and E rings of the CPT core structure. These modifications aim to improve the efficacy, selectivity, and pharmacokinetic properties of CPT derivatives. The article reviews the advancements in hybridizing CPT with other bioactive compounds, the synthesis of novel CPT analogs, and their associated biological activities. Moreover, the structure-activity relationship (SAR) of these modified CPT derivatives is summarized to gain insights into their structure-function correlations. In addition to discussing the modifications and biological activities of CPT derivatives, the article also touches upon the mechanism of parent drug release. Many CPT derivatives are prodrugs, meaning they require metabolic activation to generate the active form of the drug. It is a resource for researchers interested in developing novel anti-tumor agents based on CPT, addressing the limitations associated with the parent drug, and exploring various aspects of CPT modifications.

Synthesis of the diazatricycloundecane scaffold via gold(I)-catalysed Conia-ene-type 5-exo-dig cyclization and stepwise substituent assembly for the construction of an sp3-rich compound library

The bridged diazatricycloundecane sp3-rich scaffold was synthesised via the gold(I)-catalysed Conia-ene reaction. The electron-donating property of the siloxymethyl group on alkyne 1 enabled 6-endo-dig cyclization, whereas the ethoxy carbonyl group on alkyne 4 led to 5-exo-dig cyclization with complete regioselectivity in the Conia-ene reaction. The resulting bridged diazatricycloundecane scaffold 5 allowed the construction of a library of sp3-rich compounds. Among the compounds synthesised, compounds 6e and 6f inhibited the hypoxia inducible factor 1 (HIF-1) downstream signaling pathway without affecting HIF-1α mRNA expression.

Natural product inspired leads in the discovery of anticancer agents: an update

Natural products have emerged as major leads for the discovery and development of new anti-cancer drugs. The plant-derived anti-cancer drugs account for approximately 60% and the quest for new anti-cancer agents is in progress. Anti-cancer leads have been isolated from plants, animals, marine organisms, and microorganisms from time immemorial. The process of semisynthetic modifications of the parent lead has led to the generation of new anti-cancer agents with improved therapeutic efficacy and minimal side effects. The various chemo-informatics tools, bioinformatics, high-throughput screening, and combinatorial synthesis are able to deliver the new natural product lead molecules. Plant-derived anticancer agents in either late preclinical development or early clinical trials include taxol, vincristine, vinblastine, topotecan, irinotecan, etoposide, paclitaxel, and docetaxel. Similarly, anti-cancer agents from microbial sources include dactinomycin, bleomycin, mitomycin C, and doxorubicin. In this review, we highlighted the importance of natural products leads in the discovery and development of novel anti-cancer agents. The semisynthetic modifications of the parent lead to the new anti-cancer agent are also presented. Further, the leads in the preclinical settings with the potential to become effective anticancer agents are also reviewed.Communicated by Ramaswamy H. Sarma.

Phytochemical Analysis of Nothapodytes tomentosa and Distribution and Content of Camptothecin and its Analogues in Four Plants

Camptothecin (CPT) and its derivatives have attracted worldwide attention because of their notable anticancer activity. However, the growing demand for CPT in the global pharmaceutical industry has caused a severe shortage of CPT-producing plant resources. In this study, phytochemical analysis of Nothapodytes tomentosa results in the isolation and identification of CPT (13: ) and 16 analogues (1:  - 12, 14:  - 17: ), including a new (1: ) and five known (9, 10, 12, 15: , and 17: ) CPT analogues with an open E-ring. In view of the potential anticancer activity of CPT analogues with an open E-ring, the fragmentation pathways and mass spectra profiles of these six CPT analogues (1, 9, 10, 12, 15: , and 17: ) are investigated, providing a reference for the rapid detection of these compounds in other plants. Furthermore, based on the fragmentation patterns of CPT (13: ) and known analogues (2:  - 8, 11, 14, 16, 18:  - 26: ), the distribution and content of these compounds in different tissues of N. tomentosa, N. nimmoniana, Camptotheca acuminata, and Ophiorrhiza japonica are further studied. Our findings not only provide an alternative plant resource for further expanding the development and utilization of CPT and its analogues, but also lay a foundation for improving the utilization of known CPT-producing plant resources.

Highly Sensitive Cyanine Dyes for Rapid Sensing of NAD(P)H in Mitochondria and First-Instar Larvae of Drosophila melanogaster

We have developed two highly sensitive cyanine dyes, which we refer to as probes A and B. These dyes are capable of quick and sensitive sensing of NAD(P)H. The dyes were fabricated by connecting benzothiazolium and 2,3-dimethylnaphtho[1,2-d]thiazol-3-ium units to 3-quinolinium through a vinyl bond. In the absence of NAD(P)H, both probes have low fluorescence and absorption peaks at 370 and 400 nm, correspondingly. This is because of their two electron-withdrawing acceptor systems with high charge densities. However, when NAD(P)H reduces the probes' electron-withdrawing 3-quinolinium units to electron-donating 1,4-dihydroquinoline units, the probes absorb at 533 and 535 nm and fluoresce at 572 and 586 nm for A and B correspondingly. This creates well-defined donor-π-acceptor cyanine dyes. We successfully used probe A to monitor NAD(P)H levels in live cells during glycolysis, under hypoxic conditions induced by CoCl2 treatment and after treatment with cancer drugs, including cisplatin, camptothecin, and gemcitabine. Probe A was also employed to visualize NAD(P)H in Drosophila melanogaster first-instar larvae. We observed an increase in NAD(P)H levels in A549 cancer cells both under hypoxic conditions and after treatment with cancer drugs, including cisplatin, camptothecin, and gemcitabine.

Reversibly "double locked" hydroxycamptothecin prodrug nanoparticles for targeted chemotherapy of lung cancer

Prodrug assembled nanoparticles integrate the merits of both prodrug and nanoparticle, which significantly improve pharmacokinetic parameters, enhance tumorous accumulation and decrease adverse effects, while they are challenged by disassembly upon dilution in blood, masking the superiority of nanoparticles (NPs). Herein, a reversibly "double locked" hydroxycamptothecin (HCPT) prodrug nanoparticle decorated with cyclic RGD peptide (cRGD) is developed for safe and efficient chemotherapy of orthotopic lung cancer in mice. HCPT prodrug is constructed from acetal (ace)-linked cRGD-PEG-ace-HCPT-ace-acrylate polymer, which is self-assembled into the nanoparticles with "the first lock" of HCPT. Then the nanoparticles undergo the in situ UV-crosslinking of the acrylate residues for constructing "the second lock" of HCPT. The obtained "double locked" nanoparticles (T-DLHN) with simple and well-defined construction are demonstrated to possess extremely high stability against 100-fold dilution and acid-triggered "unlock" including de-crosslinking and liberation of the pristine HCPT. In an orthotopic lung tumor of mouse model, T-DLHN reveals a prolonged circulation time of about 5.0 h, superb lung tumor-homing capacity with tumorous drug uptake of about 7.15%ID/g, resulting in significantly boosted anti-tumor activity and reduced adverse effects. Hence, these nanoparticles utilizing "double lock" and acid-triggered "unlock" strategies represent a unique and promising nanoplatform for safe and efficient drug delivery. STATEMENT OF SIGNIFICANCE: Prodrug assembled nanoparticles have the unique properties of the well-defined structure, systemic stability, improved pharmacokinetics, passive targeting and decreased adverse effects. However, prodrug assembled NPs would disassemble against extensive dilution in the blood circulation when intravenously injected into the body. Herein, we have designed a cRGD-directed reversibly "double-locked" HCPT prodrug nanoparticle (T-DLHN) for safe and efficient chemotherapy of orthotopic A549 human lung tumor xenografts. Upon intravenous injection, T-DLHN can overcome the shortcoming of disassembly against extensive dilution, prolong the circulation time due to the "double locked" configuration and then mediate targeted drug delivery into the tumors. After uptaken into the cells, T-DLHN undergoes concurrent de-crosslinking and liberation of HCPT under acidic condition for enhanced chemotherapeutic efficacy with negligible adverse effects.

Challenges and opportunities for improving the druggability of natural product: Why need drug delivery system?

Bioactive natural products (BNPs) are the marrow of medicinal plants, which are the secondary metabolites of organisms and have been the most famous drug discovery database. Bioactive natural products are famous for their enormous number and great safety in medical applications. However, BNPs are troubled by their poor druggability compared with synthesis drugs and are challenged as medicine (only a few BNPs are applied in clinical settings). In order to find a reasonable solution to improving the druggability of BNPs, this review summarizes their bioactive nature based on the enormous pharmacological research and tries to explain the reasons for the poor druggability of BNPs. And then focused on the boosting research on BNPs loaded drug delivery systems, this review further concludes the advantages of drug delivery systems on the druggability improvement of BNPs from the perspective of their bioactive nature, discusses why BNPs need drug delivery systems, and predicts the next direction.

Interaction of an anticancer benzopyrane derivative with DNA: Biophysical, biochemical, and molecular modeling studies

BACKGROUND

SIMR1281 is a potent anticancer lead candidate with multi- target activity against several proteins; however, its mechanism of action at the molecular level is not fully understood. Revealing the mechanism and the origin of multitarget activity is important for the rational identification and optimization of multitarget drugs.

METHODS

We have used a variety of biophysical (circular dichroism, isothermal titration calorimetry, viscosity, and UV DNA melting), biochemical (topoisomerase I & II assays) and computational (molecular docking and MD simulations) methods to study the interaction of SIMR1281 with duplex DNA structures.

RESULTS

The biophysical results revealed that SIMR1281 binds to dsDNA via an intercalation-binding mode with an average binding constant of 3.1 × 10⁶ M^-1. This binding mode was confirmed by the topoisomerases' inhibition assays and molecular modeling simulations, which showed the intercalation of the benzopyrane moiety between DNA base pairs, while the remaining moieties (thiazole and phenyl rings) sit in the minor groove and interact with the flanking base pairs adjacent to the intercalation site.

CONCLUSIONS

The DNA binding characteristics of SIMR1281, which can disrupt/inhibit DNA function as confirmed by the topoisomerases' inhibition assays, indicate that the observed multi-target activity might originate from ligand intervention at nucleic acids level rather than due to direct interactions with multiple biological targets at the protein level.

GENERAL SIGNIFICANCE

The findings of this study could be helpful to guide future optimization of benzopyrane-based ligands for therapeutic purposes.

A quinoline alkaloid potentially modulates the amyloidogenic structural transitions of the biofilm scaffolding small basic protein

Bacterial biofilm formation by communities of opportunistic bacterial pathogens like Staphylococcus epidermidis is regarded as the primary virulence mechanism facilitating the spread of detrimental nosocomial and implant-associated infections. An 18-kDa small basic protein (Sbp) and its amyloid fibrils account for strengthening the biofilm architecture and scaffolding the S. epidermidis biofilm matrix. Our study reports systematic analysis of the amyloidogenic structural transitions of Sbp and predicts the amyloid core of the protein which may trigger misfolding and aggregation. Herein, we report the novel amyloid inhibitory potential of Camptothecin, a quinoline alkaloid which binds stably to Sbp monomers and redirects the formation of unstructured regions further destabilizing the protein. Molecular dynamics simulations reveal that Camptothecin averts β-sheet transitions, interrupts with electrostatic interactions and disrupts the intermolecular hydrophobic associations between the exposed hydrophobic amyloidogenic regions of Sbp. Collectively, our study puts forward the first report detailing the heteromolecular associations and amyloid modulatory effects of Camptothecin which may serve as a structural scaffold for the tailored designing of novel drugs targeting the S. epidermidis biofilm matrix.Communicated by Ramaswamy H. Sarma.

Genetic and epigenetic control of the plant metabolome

Plant metabolites are mainly produced through chemical reactions catalysed by enzymes encoded in the genome. Mutations in enzyme-encoding or transcription factor-encoding genes can alter the metabolome by changing the enzyme's catalytic activity or abundance, respectively. Insertion of transposable elements into non-coding regions has also been reported to affect transcription and ultimately metabolite content. In addition to genetic mutations, transgenerational epigenetic variations have also been found to affect metabolic content by controlling the transcription of metabolism-related genes. However, the majority of cases reported so far, in which epigenetic mechanisms are associated with metabolism, are non-transgenerational, and are triggered by developmental signals or environmental stress. Although, accumulating research has provided evidence of strong genetic control of the metabolome, epigenetic control has been largely untouched. Here, we provide a review of the genetic and epigenetic control of metabolism with a focus on epigenetics. We discuss both transgenerational and non-transgenerational epigenetic marks regulating metabolism as well as prospects of the field of metabolic control where intricate interactions between genetics and epigenetics are involved.

Camptothecin-Loaded and Manganese Dioxide-Coated Polydopamine Nanomedicine Used for Magnetic Resonance Imaging Diagnosis and Chemo-Photothermal Therapy for Lung Cancer

Introduction

Camptothecin (CPT) is a cytotoxic quinolone alkaloid (isolated from a traditional Chinese medicine Camptotheca acuminata), used for the treatment of various malignancies, which inhibits DNA topoisomerase I (Topo I). However, its drawbacks, such as poor water solubility, stability, and highly toxic side effects, limit its clinical application. Therefore, CPT needs to be prepared as a nanomedicine to improve solubility, reduce side effects, and synergize with other therapies to improve efficacy.

Methods

In this work, we constructed CPT NPs (nanoparticles), which were CPT-loaded and manganese dioxide (MnO₂)-coated polydopamine (PDA) nanomedicine. In vitro, we explored the antitumor effect including CPT NPs-induced cell proliferation inhibition, apoptosis and ferroptosis for tumor cell lines. In vivo, we established LLC tumor-bearing mice model to evaluate their tumor imaging and anticancer effects.

Results

CPT NPs improve the water solubility and stability of CPT and reduce its toxic effects. It has good biocompatibility, excellent photothermal conversion ability for photothermal therapy (PTT) and pH release in the tumor microenvironment. It can inhibit tumor cell proliferation, induce apoptosis and result in ferroptosis of tumor cells. More significantly, this nanomedicine can provide information for the location and diagnosis of tumors via magnetic resonance imaging. In general, the nanomedicine integrated with diagnosis and treatment has excellent anticancer effect.

Discussion

Altogether, this nanomedicine possesses the ability to diagnose and therapy through magnetic resonance imaging and chemo-photothermal therapy, respectively. In addition, the integrated diagnosis and treatment nanomedicine has potential clinical application prospects through treating lung cancer with high efficiency and low side effect. It can support the construction of related nano-delivery systems.

Design, synthesis and bioactivity evaluation of favorable evodiamine derivative scaffold for developing cancer therapy

Natural product evodiamine is one of the most privileged scaffolds in drug discovery and is suitable for derivatization, which can be conducted quickly for structure optimization and structure-activity relationship research. In this work, a comprehensive SAR study on evodiamine scaffold with N14-3'-fluorophenyl substituted was completed, and compounds with high anti-tumor activity and good inhibitory effect on Top1 and Top2 were screened out. Tested evodiamine derivatives exhibited excellent broad-spectrum anti-tumor activity. Among them, compound 8b revealed 55.15% and 55.50% inhibition for Top1 and Top2 at 25 μM, as well as 0.16 and 0.13 μM IC₅₀ value for MGC-803 and SGC-7901 cells, respectively; compound 9a revealed 70.50% and 71.81% inhibition for Top1 and Top2 at 25 μM, as well as 0.22 and 0.27 μM IC₅₀ value for MGC-803 and SGC-7901 cells, respectively. The further biological evaluation showed that they could functionally induce apoptosis, significantly arrest the cell cycle at the G2/M phase, and markedly inhibit cell proliferation, migration and invasion. In addition, compound 9a performed a tumor inhibitory rate of 36.35% and showed no apparent toxicity in vivo. Overall, these optimized protocols will advance the progression of cancer chemotherapy and can be used to expand the options for screening therapeutic cancer drugs.

Fungal Endophytes: an Accessible Source of Bioactive Compounds with Potential Anticancer Activity

Endophytes either be bacteria, fungi, or actinomycetes colonize inside the tissue of host plants without showing any immediate negative effects on them. Among numerous natural alternative sources, fungal endophytes produce a wide range of structurally diverse bioactive metabolites including anticancer compounds. Considering the production of bioactive compounds in low quantity, genetic and physicochemical modification of the fungal endophytes is performed for the enhanced production of bioactive compounds. Presently, for the treatment of cancer, chemotherapy is majorly used, but the side effects of chemotherapy are of prime concern in clinical practices. Also, the drug-resistant properties of carcinoma cells, lack of cancer cells-specific medicine, and the side effects of drugs are the biggest obstacles in cancer treatment. The interminable requirement of potential drugs has encouraged researchers to seek alternatives to find novel bioactive compounds, and fungal endophytes seem to be a probable target for the discovery of anticancer drugs. The present review focuses a comprehensive literature on the major fungal endophyte-derived bioactive compounds which are presently been used for the management of cancer, biotic factors influencing the production of bioactive compounds and about the challenges in the field of fungal endophyte research.

A Smart Theranostic Prodrug System Activated by Reactive Oxygen Species for Regional Chemotherapy of Metastatic Cancer

Metastatic cancer is difficult to cure because of its uncontrollable nature and side effects during treatment. We constructed a reactive oxygen species (ROS)-activated smart theranostic prodrug system based on an ROS active site linked with both a targeting group and an anticancer drug for efficient regional chemotherapy of metastatic cancers. The optimized prodrug (Bio-(8)-MB-CPT) with biotin as the targeting group displayed high sensitivity towards ROS and selectively targeting ability towards cervical cancer cells, showing highly efficient drug release (up to 92 %) in vitro. Bio-(8)-MB-CPT thus exerted strong toxicity towards cervical cancer cells, but unlike the parent drug (camptothecin), showed no toxicity towards normal cells. Moreover, the prodrug displayed significantly enhanced antitumor efficacy in vivo and eradicated the tumor with no obvious side effects (inhibition of the tumor reached up to 99.9 %).

Visible-light-mediated decarboxylative alkylation of 2-pyridone derivatives via a C3-selective C-H functionalization

A direct C-H functionalization approach to access C3-alkylated 2-pyridone derivatives is reported. This study utilizes N-hydroxyphthalimide (NHPI) esters of various carboxylic acids as sources of alkyl radicals by reductive cleavage under photocatalytic reaction conditions. The carbon-carbon bond formation occurred site-selectively at C3 of 2-pyridone to give the desired products in moderate to good yields. This method enables a faster access to C3-alkylated pyridone compounds which can be applied to the synthesis of small molecule drugs.

Camptothecin's journey from discovery to WHO Essential Medicine: Fifty years of promise

Nature represents a rich source of compounds used for the treatment of many diseases. Camptothecin (CPT), isolated from the bark of Camptotheca acuminata, is a cytotoxic alkaloid that attenuates cancer cell replication by inhibiting DNA topoisomerase 1. Despite its promising and wide spectrum antiproliferative activity, its use is limited due to low solubility, instability, acquired tumour cell resistance, and remarkable toxicity. This has led to the development of numerous CPT analogues with improved pharmacodynamic and pharmacokinetic profiles. Three natural product-inspired drugs, namely, topotecan, irinotecan, and belotecan, are clinically approved and prescribed drugs for the treatment of several types of cancer, whereas other derivatives are in clinical trials. In this review, which covers literature from 2015 to 2020, we aim to provide a comprehensive overview and describe efforts that led to the development of a variety of CPT analogues. These efforts have led to the discovery of potent, first-in-class chemotherapeutic agents inspired by CPT. In addition, the mechanism of action, SAR studies, and recent advances of novel CPT drug delivery systems and antibody drug conjugates are discussed.

Jasmonic acid biosynthesis by fungi: derivatives, first evidence on biochemical pathways and culture conditions for production

Jasmonic acid (JA) and its derivatives called jasmonates (JAs) are lipid-derived signalling molecules that are produced by plants and certain fungi. Beside this function, JAs have a great variety of applications in flavours and fragrances production. In addition, they may have a high potential in agriculture. JAs protect plants against infections. Although there is much information on the biosynthesis and function of JA concerning plants, knowledge on these aspects is still scarce for fungi. Taking into account the practical importance of JAs, the objective of this review is to summarize knowledge on the occurrence of JAs from fungal culture media, their biosynthetic pathways and the culture conditions for optimal JA production as an alternative source for the production of these valuable metabolites.

Chromosome-level genome assembly of Ophiorrhiza pumila reveals the evolution of camptothecin biosynthesis

Plant genomes remain highly fragmented and are often characterized by hundreds to thousands of assembly gaps. Here, we report chromosome-level reference and phased genome assembly of Ophiorrhiza pumila, a camptothecin-producing medicinal plant, through an ordered multi-scaffolding and experimental validation approach. With 21 assembly gaps and a contig N50 of 18.49 Mb, Ophiorrhiza genome is one of the most complete plant genomes assembled to date. We also report 273 nitrogen-containing metabolites, including diverse monoterpene indole alkaloids (MIAs). A comparative genomics approach identifies strictosidine biogenesis as the origin of MIA evolution. The emergence of strictosidine biosynthesis-catalyzing enzymes precede downstream enzymes' evolution post γ whole-genome triplication, which occurred approximately 110 Mya in O. pumila, and before the whole-genome duplication in Camptotheca acuminata identified here. Combining comparative genome analysis, multi-omics analysis, and metabolic gene-cluster analysis, we propose a working model for MIA evolution, and a pangenome for MIA biosynthesis, which will help in establishing a sustainable supply of camptothecin.

Endophytic Fungi: From Symbiosis to Secondary Metabolite Communications or Vice Versa?

Endophytic fungi (EF) are a group of fascinating host-associated fungal communities that colonize the intercellular or intracellular spaces of host tissues, providing beneficial effects to their hosts while gaining advantages. In recent decades, accumulated research on endophytic fungi has revealed their biodiversity, wide-ranging ecological distribution, and multidimensional interactions with host plants and other microbiomes in the symbiotic continuum. In this review, we highlight the role of secondary metabolites (SMs) as effectors in these multidimensional interactions, and the biosynthesis of SMs in symbiosis via complex gene expression regulation mechanisms in the symbiotic continuum and via the mimicry or alteration of phytochemical production in host plants. Alternative biological applications of SMs in modern medicine, agriculture, and industry and their major classes are also discussed. This review recapitulates an introduction to the research background, progress, and prospects of endophytic biology, and discusses problems and substantive challenges that need further study.

Prioritization of candidate cancer drugs based on a drug functional similarity network constructed by integrating pathway activities and drug activities

Due to the speed, efficiency, relative risk, and lower costs compared to traditional drug discovery, the prioritization of candidate drugs for repurposing against cancers of interest has attracted the attention of experts in recent years. Herein, we present a powerful computational approach, termed prioritization of candidate drugs (PriorCD), for the prioritization of candidate cancer drugs based on a global network propagation algorithm and a drug–drug functional similarity network constructed by integrating pathway activity profiles and drug activity profiles. This provides a new approach to drug repurposing by first considering the drug functional similarities at the pathway level. The performance of PriorCD in drug repurposing was evaluated by using drug datasets of breast cancer and ovarian cancer. Cross‐validation tests on the drugs approved for the treatment of these cancers indicated that our approach can achieve area under receiver‐operating characteristic curve (AUROC) values greater than 0.82. Furthermore, literature searches validated our results, and comparison with other classical gene‐based repurposing methods indicated that our pathway‐level PriorCD is comparatively more effective at prioritizing candidate drugs with similar therapeutic effects. We hope that our study will be of benefit to the field of drug discovery. In order to expand the usage of PriorCD, a freely available R‐based package, PriorCD, has been developed to prioritize candidate anticancer drugs for drug repurposing.

Novel lipophilic SN38 prodrug forming stable liposomes for colorectal carcinoma therapy

Background: SN38 (7-ethyl-10-hydroxy camptothecin), as a potent metabolite of irinotecan, is highly efficacious in cancer treatment. However, the clinical utility of SN38 has been greatly limited due to its undesirable properties, such as poor solubility and low stability.

Materials and methods: In order to overcome these weaknesses, moeixitecan, a lipophilic SN38 prodrug containing a SN-38, a trolox, a succinic acid linker, and a hexadecanol chain, was loaded into liposomal nanoparticles by ethanol injection method.

Results: Experiments showed that the moeixitecan-loaded liposomal nanoparticles (MLP) with a diameter of 105.10±1.49 nm have a satisfactory drug loading rate (90.54±0.41%), high solubility and stability, and showed sustained release of SN38. Notably, MLP exhibited better antitumor activity against human colon adenocarcinoma cells than irinotecan, a FDA-approved drug for the treatment of advanced colorectal cancer. Furthermore, xenograft model results showed that MLP outperformed irinotecan in terms of pharmacokinetics, in vivo therapeutic efficacy and safety. Finally, we used molecular dynamic simulations to explore the association between the structure of MLP and the physical and functional properties of MLP, moeixitecan molecules in MLP folded themselves inside the hydrocarbon chain of the lipid bilayer, which led an increased acyl chain order of the lipid bilayer, and therefore enhanced the lactone ring stability protecting it from hydrolysis.

Conclusion: Our MLP constructing strategy by liposome engineering technology may serve a promising universal approach for the effective and safe delivery of lipophilic prodrug.

Development of an enzyme‑linked immunosorbent assay for camptothecin

The use of camptothecin and its analogues has increased in clinical settings and in agriculture. Therefore, camptothecins and their derivatives, metabolites and degradation products are frequently found in the environment. Therefore, it is important to develop an ELISA for the quantification of camptothecins in human plasma, plants, animal tissues and other matrices. The present study developed a novel competitive indirect ELISA for camptothecin using a monoclonal antibody (MAb). In total, two haptens and various carrier proteins were tested to select the most suitable immunogen for the production of MAbs against camptothecin. Hapten 1 conjugated with keyhole limpet hemocyanin was selected for the preparation of MAb 5A3, and was used to establish a competitive indirect ELISA for camptothecin. A total of three derivatives of camptothecin used in clinical practice were examined. Topotecan showed an IC₅₀ value of 0.68 µg/ml with a detection limit of 0.19 µg/ml, belotecan showed an IC₅₀ value of 0.87 µg/ml with a detection limit of 0.22 µg/ml and irinotecan showed an IC₅₀ value of 2.85 µg/ml with a detection limit of 0.47 µg/ml. The cross-reactivity results suggested that the assay developed in the present study possessed a high sensitivity to camptothecin. Therefore, this immunoassay technique may be suitable for monitoring the levels of camptothecin in compound analysis, clinical applications, and analyses of food and environmental samples.

Redox/pH dual-stimuli responsive camptothecin prodrug nanogels for "on-demand" drug delivery

At present, chemotherapy remains to be one of the most important therapeutic approaches for malignant tumors. The tumor microenvironment(TME)-responsive intelligent drug delivery systems are still the hot research topics in delivering chemotherapeutic drugs. Camptothecin (CPT) possesses very strong antitumor activities, but its clinical application is hindered by its poor water-solubility and serious toxic side effects. Herein, a new intelligent and TME-responsive P(CPT-MAA) prodrug nanogel was developed for delivering CPT and reducing its side effects. P(CPT-MAA) prodrug nanogels were prepared with methacrylic acid (MAA), CPT monomer (CPTM) and N,N'-methylenebisacrylamide (Bis) via distillation-precipitation polymerization, in which CPT was covalently conjugated into the nanogels via redox-responsive disulfide linker. The as-prepared nanogels were spherical shapes with uniform size and narrow size distribution. With the help of redox-responsive property of disulfide linker and pH-responsive property of PMAA, the release of CPT from prodrug nanogels was redox/pH-dual dependent and could be accelerated by the increased concentration of GSH and the decreased pH value, which were favorable to realize the "on-demand" drug release in tumor cell and tumor tissue microenvironment. Furthermore, P(CPT-MAA) prodrug nanogels exhibited superior antitumor activity both in vitro and in vivo without observed side effects. Hence, the prepared P(CPT-MAA) prodrug nanogels may be a promise delivery system for chemotherapeutic agents.

Preparation and characterization of multimodal hybrid organic and inorganic nanocrystals of camptothecin and gold

We demonstrate a novel inorganic-organic crystalline nanoconstruct, where gold atoms were imbedded in the crystal lattices as defects of camptothecin nanocrystals, suggesting its potential use as simultaneous agents for cancer therapy and bioimaging. The incorporation of gold, a potential computed tomography (CT) contrast agent, in the nanocrystals of camptothecin was detected by transmission electron microscope (TEM) and further quantified by energy dispersive X-ray spectrometry (EDS) and inductively coupled plasma-optical emission spectrometers (ICP-OES). Due to gold's high attenuation coefficient, only a relatively small amount needs to be present in order to create a good noise-to-contrast ratio in CT imaging. The imbedded gold atoms and clusters are expected to share the same biological fate as the camptothecin nanocrystals, reaching and accumulating in tumor site due to the enhanced permeation and retention (EPR) effect.

Recent developments in compounds acting in the DNA minor groove

The macromolecule that carries genetic information, DNA, is considered as an exceptional target for diseases depending on cellular division of malignant cells (i.e. cancer), microbes (i.e. bacteria) or parasites (i.e. protozoa). To aim for a comprehensive review to cover all aspects related to DNA targeting would be an impossible task and, hence, the objective of the present review is to present, from a medicinal chemistry point of view, recent developments of compounds targeting the minor groove of DNA. Accordingly, we discuss the medicinal chemistry aspects of heterocyclic small-molecules binding the DNA minor groove, as novel anticancer, antibacterial and antiparasitic agents.

Synthesis, Experimental and Density Functional Theory (DFT) Studies on Solubility of Camptothecin Derivatives

Two camptothecin derivatives, 10-cyclohexyl-7-methyl-20(S)-camptothecin and 7-methyl-10-morpholino-20(S)-camptothecin, were synthesized and their differences in solubility were investigated using four chosen solvent systems. Based on our results, 10-cyclohexyl-7-methyl-20(S)-camptothecin exhibited higher solubilities than 7-methyl-10-morpholino-20(S)-camptothecin in polar aprotic solvents. However, these two camptothecin derivatives did not exhibit apparent differences in solubility between 5% dimethyl sulfoxide (DMSO)/95% normal saline co-solvent system and 5% dimethylacetamide (DMAC)/95% normal saline co-solvent system. To rationalize their differences in solubility, we also tried to perform a DFT-B3LYP study to investigate their interaction with one water molecule.

Design and synthesis of some β-carboline derivatives as multi-target anticancer agents

Aim: Some anticancer β-carbolines exhibited dual inhibition of topo-I and KSP. Methodology/Results: Novel β-carbolines were synthesized and screened for their anticancer activity according to the NCI protocol. Five dose assays results indicated that compounds 9, 10, 12, 17 and 20 were potent and non selective anticancer agents; the sulfanyltriazole 12 was the most potent. Compounds 10, 12 and 20 showed dual topo-I and KSP inhibition with compound 12 being the most potent. Active compounds elicited Pre-G1 apoptosis and cell cycle arrest at G2/M phase of melanoma MDA-MB-435 cells. Docking results, in silico physicochemical and absorption, distribution, metabolism, excretion (ADME) properties were appropriate. Conclusion: Compounds 10, 12 and 20 are potent apoptosis-inducing multitarget anticancer agents that act via dual inhibition of topo-I and KSP-ATPase.

Responses of Morphology, Gas Exchange, Photochemical Activity of Photosystem II, and Antioxidant Balance in Cyclocarya paliurus to Light Spectra

Light quality is a critical factor regulating photosynthetic capacity which directly affects the final yield of plants. Cyclocarya paliurus is a multiple function tree species and its leaves are widely used as tea production and ingredient in functional foods in China. However, the effects of varying light quality on photosynthetic process and the photoprotective mechanisms remains unexplored in-depth. In this study, the biomass accumulation, morphology changes, photosynthetic capacity, stomata ultrastructure, pigments content, PSII activity, reactive oxygen species production, antioxidant enzymes, and phenolic content of C. paliurus plants under different light-emitting diodes (LED) light treatments were investigated to test a hypothesis that the difference in photosynthetic efficiency of C. paliurus plants under differential light quality is related to the degree of photoinhibition and the activation of photoprotection. We found that C. paliurus plants performed better under the treatments of WL (white light, 445 and 560 nm) and BL (blue light, 456 nm) than the treatment of GL (green light, 514 nm) and RL (red light, 653 nm). The better performances were characterized by higher values of photosynthetic capacity, total biomass, pigments content, specific leaf mass per area, seeding height increment, leaf thickness and palisade length. In contrast, plants under the treatments of GL and RL suffered significant photoinhibition but effectively developed photoprotective mechanisms. Results of this study provide not only some insights of the response mechanisms of plant photosynthesis to light quality but also a scientific basis for improving the cultivation of C. paliurus plantations.

Topoisomerase 1B poisons: Over a half-century of drug leads, clinical candidates, and serendipitous discoveries

Topoisomerases are DNA processing enzymes that relieve supercoiling (torsional strain) in DNA, are necessary for normal cellular division, and act by nicking (and then religating) DNA strands. Type 1B topoisomerase (Top1) is overexpressed in certain tumors, and the enzyme has been extensively investigated as a target for cancer chemotherapy. Various chemical agents can act as "poisons" of the enzyme's religation step, leading to Top1-DNA lesions, DNA breakage, and eventual cellular death. In this review, agents that poison Top1 (and have thus been investigated for their anticancer properties) are surveyed, including natural products (such as camptothecins and indolocarbazoles), semisynthetic camptothecin and luotonin derivatives, and synthetic compounds (such as benzonaphthyridines, aromathecins, and indenoisoquinolines), as well as targeted therapies and conjugates. Top1 has also been investigated as a therapeutic target in certain viral and parasitic infections, as well as autoimmune, inflammatory, and neurological disorders, and a summary of literature describing alternative indications is also provided. This review should provide both a reference for the medicinal chemist and potentially offer clues to aid in the development of new Top1 poisons.

The Plant Alkaloid Camptothecin as a Novel Antifouling Compound for Marine Paints: Laboratory Bioassays and Field Trials

The extensive use of copper and booster biocides in antifouling (AF) paints has raised environmental concerns and the need to develop new AF agents. In the present study, 18 alkaloids derived from terrestrial plants were initially evaluated for AF activity using laboratory bioassays with the bryozoan Bugula neritina and the barnacle Balanus albicostatus. The results showed that 4 of the 18 alkaloids were effective in inhibiting larval settlement of B. neritina, with an EC₅₀ range of 6.18 to 43.11 μM, and 15 of the 18 alkaloids inhibited larval settlement of B. albicostatus, with EC₅₀ values ranging from 1.18 to 67.58 μM. Field trials that incorporated five alkaloids respectively into paints with 20% w/w indicated an in situ AF efficiency of evodiamine, strychnine, camptothecin (CPT), and cepharanthine, with the most potent compound being CPT, which also exhibited stronger AF efficiency than the commercial antifoulants cuprous oxide and zinc pyrithione in the field over a period of 12 months. Further field trials with different CPT concentrations (0.1 to 20% w/w) in the paints suggested a concentration-dependent AF performance in the natural environment, and the effective concentrations to significantly inhibit settlement of biofoulers in the field were ≥ 0.5% w/w (the efficiency of 0.5% w/w lasted for 2 months). Moreover, CPT toxicity against the crustacean Artemia salina, the planktonic microalgae Phaeodactylum tricornutum and Isochrysis galbana, was examined. The results showed that 24 h LC₅₀ of CPT against A. salina was 20.75 μM, and 96 h EC₅₀ (growth inhibition) values of CPT to P. tricornutum and I. galbana were 55.81 and 6.29 μM, respectively, indicating that CPT was comparatively less toxic than several commercial antifoulants previously reported. Our results suggest the novel potential application of CPT as an antifoulant.

From Oxiranes to Oligomers: Architectures of U.S. FDA Approved Pharmaceuticals Containing Oxygen Heterocycles

Oxygen heterocycles are the second most common type of heterocycles that appear as structural components of U.S. Food and Drug Administration (FDA) approved pharmaceuticals. Analysis of our database of drugs approved through 2017 reveals 311 distinct pharmaceuticals containing at least one oxygen heterocycle. Most prevalent among these are pyranoses, with furanoses, macrolactones, morpholines, and dioxolanes rounding off the top five. The main body of this Perspective is organized according to ring size, commencing with three- and four-membered rings and ending with macrocycles, polymers, and unusual oxygen-containing heterocycles. For each section, all oxygen heterocycle-containing drugs are presented along with a brief discussion about structural and drug application patterns.

Analyte-driven self-assembly of graphene oxide sheets onto hydroxycamptothecin-functionalized upconversion nanoparticles for the determination of type I topoisomerases in cell extracts

Type I topoisomerases (TOPOI), a potential diagnostic biomarker and a target for chemotherapeutic agents, play essential roles in DNA replication, transcription, chromosome segregation, and recombination. It is essential to develop analytical methods for accurate detection of TOPOI in biological fluids for early diagnosis of diseases. Here we show an assay for TOPOI on the basis of the target-induced self-assembly of graphene oxide (GO) sheets onto hydroxycamptothecin-functionalized upconversion nanoparticles (HCPT-UCNPs). The dipole-dipole coupling of HCPT-UCNPs (donor) and GO (acceptor) regulated by TOPOI enables Förster resonance energy transfer between the donor and the acceptor. Integration of minimal autofluorescence and highly specific affinity into the developed nanosensor allows reliable detection of TOPOI in the nanomolar range with the detection limit of 0.29 nM. The detection of TOPOI in breast cancer cells with recoveries from 96.3 to 103.7% shows the availability of the proposed assay in complicated samples. Graphical abstract ᅟ.

Anticancer drug discovery from Chinese medicinal herbs

Cancer is still presenting a serious threat to human health worldwide. The understanding of the complex biology of cancer and the development of oncotherapy have led to increasing treatment approaches such as targeted therapy and immunotherapy. Chinese medicinal herbs have attracted considerable attention due to their potential anticancer effects. Some natural products or formulae from Chinese medicinal herbs with directly or indirectly anticancer effects have been reported. In this article, we summarized the current progression on development of anticancer drugs from Chinese medicinal herbs, toward providing ideas for further development and application of Chinese medicinal herbs in cancer therapy.

Effect of structural factors on release profiles of camptothecin from block copolymer conjugates with high load of drug

The aim of the present work was the synthesis and study the kinetics and profiles of camptothecin (CPT) release form block co- and ter-polymer conjugates comprising polylactide (PLA) segments and CPT moieties, structurally diverse by degrees of branching, content of d-PLA units and poly(ethylene glycol) methyl ether methacrylate (PEGMA). Six PLA, non-toxic macroinitiators (MIs), terminated with α-bromoester were synthesized. MIs were subjected to polymerization of CPT methacrylic derivative (CPTMA) with PEGMA at various ratios. The average contents of CPT from elemental analysis, NMR and UV-GPC were approximate to each other. The number of CPT molecules and PEGMA units was in the range of 9-195 and 0-280 per conjugate, respectively. PEGMA units plasticized PLA causing increase of its crystallinity, whereas 7% and more of d-PLA caused material amorphous. PEGMA units decreased thermal stability of conjugates, however it compatibillized the separated phases of PLA and PCPTMA, based on AFM. In vitro release rate of CPT from linear PLA conjugates deposited on injection-molded PLA bars increased by introduction of PEGMA units with zero-order kinetics and Korsmeyer-Peppas model indicating the super case II transport. Branched conjugates revealed some burst release and then the release was rather of first-order-kinetics with respect to CPT with non-Fickian transport.

Fluorine and Fluorinated Motifs in the Design and Application of Bioisosteres for Drug Design

The electronic properties and relatively small size of fluorine endow it with considerable versatility as a bioisostere and it has found application as a substitute for lone pairs of electrons, the hydrogen atom, and the methyl group while also acting as a functional mimetic of the carbonyl, carbinol, and nitrile moieties. In this context, fluorine substitution can influence the potency, conformation, metabolism, membrane permeability, and P-gp recognition of a molecule and temper inhibition of the hERG channel by basic amines. However, as a consequence of the unique properties of fluorine, it features prominently in the design of higher order structural metaphors that are more esoteric in their conception and which reflect a more sophisticated molecular construction that broadens biological mimesis. In this Perspective, applications of fluorine in the construction of bioisosteric elements designed to enhance the in vitro and in vivo properties of a molecule are summarized.